THEORY OF OPERATION AC/DC ELECTRONIC LOAD CHROMA MODEL 63800

Transcription

1 HOMA SYSTEMS SOUTIONS, IN. WOKIN ON BETTE SOUTIONS THEOY OF OPEATION A/D EETONI OAD HOMA MODE 6800 JUNE 007 Prefce: Th documet decre the theory of operto d uque mplemetto whch hrom h employed the developmet of the Model 6800 A/D lod. The 6800 A/D od re tte-of-the-rt tet trumet deged to replce pve lod elemet to multe wde rge of ler d o-ler lodg codto. 7 hryler Irve, A tel fx Pge of 0

2 HOMA SYSTEMS SOUTIONS, IN. WOKIN ON BETTE SOUTIONS Smulto of Pve ectfed od AOAD 6804 Forwrd Whe tetg A ource, geertor or Uterruptle Power Supply UPS, the output voltge d curret chrctertc hve to e meured whe the output loded. The lod my e pve retor, ductor, cpctor or comto. The retce, ductce d cpctce c e dfferet from pplcto to pplcto. oequetly, t del to hve lod devce tht cple to djutg the vlue of vrou compoet. However, th very dffcult to mplemet. To cheve th ug pve elemet, the devce would eed to hve coutle wtche, retor, ductor d cpctor to multe ll dered crcut. Other prolem wth pve elemet re hgh power dpto d poor temperture coeffcet, mg fe lodg djutmet lmot mpole, or too cotly. Therefore, covetol lod devce ue fewer compoet d wtche d provde very lmted lod multo cplty The dutry h log ee wtg for ctve lod whch cple of wde rge of multo vlue to cree tet coverge d gve more vlule meuremet. hrom 6800 A/D lod hve ee deged to provde off-the-helf oluto for rel world lod multo d meuremet. 7 hryler Irve, A tel fx Pge of 0 Theory of Operto There re 8 operto mode vlle for hrom 6800: mode, mode, P mode, mode, -P mode, D mode, D-ET mode d INUSH mode. Ech mode h dfferet equvlet crcut. Uer my elect dfferet lod mode e o the output chrctertc of the ut uder tet.. mode Fg. A ee Fg., th lod mode provde cott curret multo. Whe the lodg curret d relevt prmeter were et, 6800 wll drw curret e o the uer ettg d dregrd the output voltge of the UUT. I th mode, t equvlet A mpedce theoretclly ftely hgh. Thu, the UUT ee ftely hgh A mpedce wth the defed dwdth from the lod. If oe wt to drw curret from UUT wthout multg the lod mpedce effect, the mode the del mode. I Fg, Z o jx the output mpedce of the UUT, the voltge d curret wveform whch reult re how Fg.. The crcle hghlght the voltge dtorto

3 HOMA SYSTEMS SOUTIONS, IN. WOKIN ON BETTE SOUTIONS whch cued y the output mpedce of the UUT. The curret predefed uodl wve.. P mode Sme Fg., ut the P mode llow uer to et the lodg power d relevt prmeter rther th lodg curret, the E-lod wll the lod the UUT t cott power level. However, dffer from mode, the lodg curret relevt to the UUT output voltge to eep cott power mer. The A mpedce ee for UUT from E-lod me the mode.. mode Fg. 4. D mode There re four u-operto mode for D lod multo. They re,, & P mode. Ther operto d lodg effect re the me tem - metoed ove. mode mlr to mode except the UUT voltge wll e meured to determe the lodg curret. Fg. 5. D-ET mode Fg. how equvlet crcut mode. It qute trght forwrd tht uer et the lod retce d the E-lod wll follow. Uder mode, the lodg curret wll e proportol to the UUT output voltge d the rto of the voltge d lodg curret wll the e the progrmmed retce. Uder mode, the UUT ee cott retce wth defed dwdth from the E-lod whch equl to the ettg vlue. To me t mple, t le coectg retor o the UUT output wth retve lodg effect. Fg.4 7 hryler Irve, A tel fx Pge of 0

4 HOMA SYSTEMS SOUTIONS, IN. WOKIN ON BETTE SOUTIONS 6. mode Fg.6 Fg.5 UPS devce deged to delver fed curret commoly ourced y mot of the pplce coected to them. Mot UPS deger ue retve lod whe tetg the Power Fctor oro PF crcut thu the lodg curret cloe to D. Th doe ot reflect the rel crcut pplcto where the lodg curret fct how fed ptter. A ee Fg.4 mplfed PF crcut whe ug D lod, the output rpple curret cot e predcted thu the vlue of & c t e defed. hrom 6800 provde fed lodg ychroou to the m frequecy gvg rel lod multo d meuremet. Fg.4 lo how coecto of two lod to PF crcut to multe oth potve I d egtve I, hlf crcle fed curret. Fg.5 how the wveform of the m voltge d I, I. Note tht the phe of the I & I c e mpulted uder D-ET mode. 7 hryler Irve, A tel fx Pge 4 of 0 Fg.7 Th the le of hrom 6804 A/D lod. There o mlr product vlle the feld. Fg.6 how the equvlet crcut of UUT d fed lod crcut. The teto of mode to replce thoe pve compoet, r,,, d dode. Ug ophtcte lgorthm d hgh peed DSP, the 6804 cple to clculte the rel tme lodg curret e o UUT output voltge d r,,, ettg. Detl wll e decred lter. A ee Fg.6, the ere retor r, ormlly dded to elmte the ruh curret. Sometme wll e dded to cree the power fctor. The UUT A Source or UPS h output mpedce Z o, o we my mplfy the equvlet crcut Fg.7 for

5 HOMA SYSTEMS SOUTIONS, IN. WOKIN ON BETTE SOUTIONS DSP clculto. I Fg.7, r; x. the rel retve prt of Z o Fg.6, d x trformed from jx whch the mgry ve prt of Z o Fg.6. Before the ctul lod curret ppled, The E-lod wll detect the Z o of the UUT, the come wth compoet vlue et y uer, the DSP wll e le to clculte the lodg curret. Fg P mode Uder mode, whe the UUT output voltge r.m.. vryg, the lodg curret r.m.. wll vry too ccordg to Ohm lw wll output power. However, mot UUT tet pl pecfy power rtg rther th compoet vlue of the fy lod devce. The -P mode deged to mplfy uer ettg wth the eed for detl lod formto. I th mode, uer oly eed to et the power d power fctor of the lod, the DSP wll clculte the et oluto d gve pproprte,, vlue to mt the power d power fctor fter lod o. -mode lculto & Aly There re two wy to get the mode lodg curret. Frt to clculte the dfferetl, tegrto ug log pproch. The ecod to covert the frequecy-dom trfer fucto to dgted trfer fucto the clculte t uder tme-dom. The 6804 ue ecod pproch therefore we focu o tht d elorte the proce elow. Be o operto rego of the dode, two clculto re decred repectvely: 8. INUSH mode mode multe oly tedy-tte d doe t provde tret curret uch ruh curret ee rel pplcto. To multe ruh curret, 6800 provde INUSH mode. I INUSH mode, the E-lod wll multe oly oe-cycle lod multo ecue relty, the curret of the fy crcut wll e tle fter oe cycle. The mxmum pe curret 00A. Fg.8 how the ruh wveform. Fg.9. Dode forwrd ed: See equvlet crcut Fg.9 top. If defe The tl voltge cro cpctor 7 hryler Irve, A tel fx Pge 5 of 0

6 HOMA SYSTEMS SOUTIONS, IN. WOKIN ON BETTE SOUTIONS 7 hryler Irve, A tel fx Pge 6 of 0 whe the dode out to e ON. f r eferece frequecy f Smplg frequecy We c get / cot r r f f f π π I 4 4 Y X X Y By ug ler trformto, we my covert log trfer fucto ~ 4 to dgtl trfer fucto H ~ H 4. Thu we get 0 H A 0 / A / A / A / A / ] [ A 0 H 0 / A 0 / A 0 H 0 / A / A / A H A 40 [ / ] A 4 [ ]/ A 4 [ ]/ A 4 [ / ] A [ 4 ]/ A [ 4 ]/ A [ 4 ]/ A From ove, we my derve the curret d voltge fucto follow: 0 I 0 I I Ug the fucto ove, we my the

7 HOMA SYSTEMS SOUTIONS, IN. WOKIN ON BETTE SOUTIONS clculte the multeou I & vlue.. Dode revere ed: See equvlet crcut Fg 9 dow. If f The voltge cro cpctor whe the dode OFF. We c get 5 f 5 Ug the me dgtl covero, we get: H A 50 / A 5 / A 5 / A 5 50 f 5 f Fg.0 Below how few exmple uder dfferet put voltge d ettg. Fg. plotted e o followg codto & ettg: 0 /60 H 50 mω 9 uh 0000 uf 5Ω We my ue ove fucto to clculte the whle the dode off-tte. Durg the clculto proce, the I & wll e ued to determe whe the dode hould e ON d whe t hould e OFF. The voltge wveform howed Fg.0 the wveform of the dode put; curret wveform the lodg curret wveform. Fg. Sce the pretty mll, o we ee the curret phe led the voltge lghtly. Fg. how other et of wveform uder dfferet ettg. odto & Settg for Fg.: 0 /60 H 50mΩ 00 uh 0000 uf 5Ω 7 hryler Irve, A tel fx Pge 7 of 0

8 HOMA SYSTEMS SOUTIONS, IN. WOKIN ON BETTE SOUTIONS ght here, the curret phe lc of voltge ecue hgher et. Fg. From Fg., Fg., we ow, hve drmtc mpct to the curret phe d wve-hpe. Fg. h hgher ret Fctor. I cotrt, Fg. h hgher Power Fctor. Aother otcele dfferece etwee mode d mode : The curret wve-hpe mode uodl ut mode ot. Although the dfferece ot very g; ut t repreet dfferet lodg tre to the UUT. Uder mode, wht UUT ee from E-lod fte hgh mpedce ut uder mode, t comto of r,,, tht reflect the rel pplcto cero. The UUT ormlly h t ow cotrol loop; the output mpedce wll fluece the cloe loop g & phe d evetully the ytem tlty. hrom 6804 d t mode my multe the pve compoet thu vod ocllto tht commoly ee o trdtol A lod deg. ocluo mode worg y ug rel tme clculto of DSP. Whe the Smplg 7 hryler Irve, A tel fx Pge 8 of 0 frequecy of the DSP d curret mplfer dwdth re fte hgh, d the clculto tme queeed dow to ero, t operto lterlly me log crcut. The meuremet reult wll the e detcl. However, the hrdwre mplg rte h t lmt; the clculto tme c t e ero; plu the UUT output mpedce ductce wll lmt the curret mplfer dwdth d lo the cotrol dely ue; thee me the Power Fctor, ret Fctor, Power d curret my e lghtly dfferet from the ctul pve compoet crcut. But, the wveform d repoe wll tll e the me. But, to me prctcl ue, the UUT output frequecy lmted to 70H. For frequecy hgher th 70H, the error ecome too hgh to gore thu mode o loger recommeded. I th ce, uer my elect other lod mode for lod multo. Below re two exmple tht how the lodg wveform y ug ctul pve compoet crcut d lodg wveform multed y ug mode of hrom Ex : Tet odto: A ource Output Impedce: o 50mΩ; o 9uH 0 uh r 0Ω.5Ω 4800 uf

9 HOMA SYSTEMS SOUTIONS, IN. WOKIN ON BETTE SOUTIONS A 0 / 60 H multed wveform y ug Fg. how the wveform of ctul pve compoet crcut d Fg.4 how the multed wveform y ug Fg.5 Fg. Fg.4 Ex : Tet odto: A ource Output Impedce: o 50mΩ; o 9uH 00 uh r 0Ω.5Ω 4800 uf A 0 / 60 H Fg.5 the wveform of ctul pve compoet crcut d Fg.6 how the 7 hryler Irve, A tel fx Pge 9 of 0 Fg.6 A ee from the wveform, hrom 6800 multed lodg wveform re lmot detcl to the ctul pve compoet crcut, jut very mll uvodle dely potted whoe reo w elorted erler dcuo. If the UUT equvlet output ductce o 00 uh ut the ere ductce of the lod 0; the voltge wveform wll e hghly dtorted how Fg.7. Th cued y the drop over o of the UUT uder lodg. A we c ee from Fg., whe the o of UUT low, eve the lodg curret tll hgh, ut

10 HOMA SYSTEMS SOUTIONS, IN. WOKIN ON BETTE SOUTIONS very mll voltge dtorto c e oerved. Fg.7 For more formto relted to hrom 6800 Sere A/D lod, the compy d other tet oluto, plee go to: 7 hryler Irve, A tel fx Pge 0 of 0